Common-substrate semiconductor devices having nanowires or semiconductor bodies with differing material orientation or composition

ABSTRACT

Common-substrate semiconductor devices having nanowires or semiconductor bodies with differing material orientation or composition and methods to form such common-substrate devices are described. For example, a semiconductor structure includes a first semiconductor device having a first nanowire or semiconductor body disposed above a crystalline substrate. The first nanowire or semiconductor body is composed of a semiconductor material having a first global crystal orientation. The semiconductor structure also includes a second semiconductor device having a second nanowire or semiconductor body disposed above the crystalline substrate. The second nanowire or semiconductor body is composed of a semiconductor material having a second global crystal orientation different from the first global orientation. The second nanowire or semiconductor body is isolated from the crystalline substrate by an isolation pedestal disposed between the second nanowire or semiconductor body and the crystalline substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/996,506, filed on Jun. 20, 2013, which is a U.S. National Phaseapplication under 35 U.S.C. §371 of International Application No.PCT/US2011/067242, filed Dec. 23, 2011, entitled “COMMON-SUBSTRATESEMICONDUCTOR DEVICES HAVING NANOWIRES OR SEMICONDUCTOR BODIES WITHDIFFERING MATERIAL ORIENTATION OR COMPOSITION,” the entire contents ofwhich are incorporated herein by reference.

TECHNICAL FIELD

Embodiments of the invention are in the field of semiconductor devicesand, in particular, common-substrate semiconductor devices havingnanowires or semiconductor bodies with differing material orientation orcomposition and methods to form such common-substrate devices.

BACKGROUND

For the past several decades, the scaling of features in integratedcircuits has been a driving force behind an ever-growing semiconductorindustry. Scaling to smaller and smaller features enables increaseddensities of functional units on the limited real estate ofsemiconductor chips. For example, shrinking transistor size allows forthe incorporation of an increased number of memory devices on a chip,lending to the fabrication of products with increased capacity. Thedrive for ever-more capacity, however, is not without issue. Thenecessity to optimize the performance of each device becomesincreasingly significant.

Maintaining mobility improvement and short channel control asmicroelectronic device dimensions scale past the 15 nanometer (nm) nodeprovides a challenge in device fabrication. Nanowires used to fabricatedevices provide improved short channel control. For example, silicongermanium (Si_(x)Ge_(1-x)) nanowire channel structures (where x<0.5)provide mobility enhancement at respectable Eg, which is suitable foruse in many conventional products which utilize higher voltageoperation. Furthermore, silicon germanium (Si_(x)Ge_(1-x)) nanowirechannels (where x>0.5) provide mobility enhanced at lower Egs (suitablefor low voltage products in the mobile/handheld domain, for example.Many different techniques have been attempted to fabricate and optimizenanowire-based devices. However, significant improvements are stillneeded in the area of nanowire devices.

In the manufacture of integrated circuit devices, multi-gatetransistors, such as tri-gate transistors, have become more prevalent asdevice dimensions continue to scale down. In conventional processes,tri-gate transistors are generally fabricated on either bulk siliconsubstrates or silicon-on-insulator substrates. In some instances, bulksilicon substrates are preferred due to their lower cost and becausethey enable a less complicated tri-gate fabrication process. In otherinstances, silicon-on-insulator substrates are preferred because of theimproved short-channel behavior of tri-gate transistors.

On bulk silicon substrates, the fabrication process for tri-gatetransistors often encounters problems when aligning the bottom of themetal gate electrode with the source and drain extension tips at thebottom of the transistor body (i.e., the “fin”). When the tri-gatetransistor is formed on a bulk substrate, proper alignment is needed foroptimal gate control and to reduce short-channel effects. For instance,if the source and drain extension tips are deeper than the metal gateelectrode, punch-through may occur. Alternately, if the metal gateelectrode is deeper than the source and drain extension tips, the resultmay be an unwanted gate cap parasitics. Many different techniques havebeen attempted to fabricate and optimize three-dimensional devices.However, significant improvements are still needed in the area ofthree-dimensional semiconductor devices.

SUMMARY

Embodiments of the present invention include common-substratesemiconductor devices having nanowires or semiconductor bodies withdiffering material orientation or composition and methods to form suchcommon-substrate devices.

In an embodiment, a semiconductor structure includes a firstsemiconductor device having a first nanowire disposed above acrystalline substrate. The first nanowire is composed of a semiconductormaterial having a first global crystal orientation. The semiconductorstructure also includes a second semiconductor device having a secondnanowire disposed above the crystalline substrate. The second nanowireis composed of a semiconductor material having a second global crystalorientation different from the first global orientation. The secondnanowire is isolated from the crystalline substrate by an isolationpedestal disposed between the second nanowire and the crystallinesubstrate.

In another embodiment, a semiconductor structure includes a firstsemiconductor device having a first nanowire disposed above acrystalline substrate. The first nanowire is composed of a firstsemiconductor material. The semiconductor structure also includes asecond semiconductor device having a second nanowire disposed above thecrystalline substrate. The second nanowire is composed of a secondsemiconductor material different from the first semiconductor material.The second nanowire is isolated from the crystalline substrate by anisolation pedestal disposed between the second nanowire and thecrystalline substrate.

In another embodiment, a semiconductor structure includes a firstsemiconductor device having a first semiconductor body disposed above acrystalline substrate. The first semiconductor body is composed of asemiconductor material having a first global crystal orientation. Thesemiconductor structure also includes a second semiconductor devicehaving a second semiconductor body disposed above the crystallinesubstrate. The second semiconductor body is composed of a semiconductormaterial having a second global crystal orientation different from thefirst global orientation. The second semiconductor body is isolated fromthe crystalline substrate by an isolation pedestal disposed between thesecond semiconductor body and the crystalline substrate.

In another embodiment, a semiconductor structure includes a firstsemiconductor device having a first semiconductor body disposed above acrystalline substrate. The first semiconductor body is composed of afirst semiconductor material. The semiconductor structure also includesa second semiconductor device having a second semiconductor bodydisposed above the crystalline substrate. The second semiconductor bodyis composed of a second semiconductor material different from the firstsemiconductor material. The second semiconductor body is isolated fromthe crystalline substrate by an isolation pedestal disposed between thesecond semiconductor body and the crystalline substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a three-dimensional cross-sectional view ofnanowire-based semiconductor devices, in accordance with an embodimentof the present invention.

FIG. 1B illustrates a cross-sectional view of a nanowire-basedsemiconductor device of FIG. 1A, as taken along the a-a′ axis, inaccordance with an embodiment of the present invention.

FIG. 1B′ illustrates a cross-sectional view of another nanowire-basedsemiconductor device of FIG. 1A, as taken along the a-a′ axis, inaccordance with another embodiment of the present invention.

FIGS. 2A-2J illustrate cross-sectional views representing variousoperations in a method of fabricating a nanowire semiconductorstructure, in accordance with an embodiment of the present invention.

FIGS. 3A-3K illustrate cross-sectional views representing variousoperations in a method of fabricating another nanowire semiconductorstructure, in accordance with another embodiment of the presentinvention.

FIG. 4A illustrates a three-dimensional cross-sectional view ofsemiconductor body-based semiconductor devices, in accordance with anembodiment of the present invention.

FIG. 4B illustrates a cross-sectional view of a semiconductor body-basedsemiconductor device of FIG. 4A, as taken along the a-a′ axis, inaccordance with an embodiment of the present invention.

FIG. 4B′ illustrates a cross-sectional view of another semiconductorbody-based semiconductor device of FIG. 4A, as taken along the a-a′axis, in accordance with another embodiment of the present invention.

FIGS. 5A-5I illustrate cross-sectional views representing variousoperations in a method of fabricating a semiconductor body-basedsemiconductor structure, in accordance with an embodiment of the presentinvention.

FIGS. 6A-6I illustrate cross-sectional views representing variousoperations in a method of fabricating another semiconductor body-basedsemiconductor structure, in accordance with another embodiment of thepresent invention.

FIG. 7 illustrates exemplary process flows for forming a wafer having acrystalline substrate and one or more separate crystalline activelayers, in accordance with an embodiment of the present invention.

FIG. 8 illustrates a computing device in accordance with oneimplementation of the invention.

DETAILED DESCRIPTION

Common-substrate semiconductor devices having nanowires or semiconductorbodies with differing material orientation or composition and methods toform such common-substrate devices are described. In the followingdescription, numerous specific details are set forth, such as specificnanowire or semiconductor body integration and material regimes, inorder to provide a thorough understanding of embodiments of the presentinvention. It will be apparent to one skilled in the art thatembodiments of the present invention may be practiced without thesespecific details. In other instances, well-known features, such asintegrated circuit design layouts, are not described in detail in orderto not unnecessarily obscure embodiments of the present invention.Furthermore, it is to be understood that the various embodiments shownin the Figures are illustrative representations and are not necessarilydrawn to scale.

One or more embodiments described herein are targeted at transistorfabrication having different active regions (also described as differentsubstrates) on the same production wafer. For example, in oneembodiment, an under fin oxidation (UFO) technique is used to integratefins or wires on different substrates on the same wafer. The processflows described herein may be applicable to tri-gate and fin-FETtransistors, e.g., for the 14 nanometer node and beyond. Embodiments mayinclude processing a silicon-on-insulator (SOI) wafer with differentsubstrates separated by a buried oxide (BOX) layer. Using a UFOapproach, the integration of transistors on different substrates, onenext to another, may be achieved. Improve performance for transistorsmay be achieved by reducing standby leakage which may be especiallycritical to 14 nanometer node system on a chip (SOC) products withextremely stringent standby power requirements.

Current semiconductor processing often requires p-MOS and n-MOS devicesbe fabricated from the same starting material and crystal orientation.Instead, in accordance with an embodiment of the present invention, themost suitable transistor properties of different channel materialsand/or orientations for each polarity of device may be used on the samewafer. Additionally, building fin-FETs or tri-gate devices on fins witha buried oxide layer or an isolation pedestal may be used to isolate theactive fin channel from the underlying substrates. Thus, the integrationof different substrates on the same wafer for fins and wire processes isdescribed below. For example, in one embodiment, one type of substrate,e.g., (100) Si or III-V on (111), for nMOS, and another type, e.g.,(110) Si, for PMOS are fabricated on the same wafer.

Thus, in a first aspect, devices with nanowire crystal orientation ormaterial composition modulation on a common substrate are provided byapproaches described herein. In an example, FIG. 1A illustrates athree-dimensional cross-sectional view of nanowire-based semiconductordevices 100 and 100′, in accordance with an embodiment of the presentinvention. FIG. 1B illustrates a cross-sectional view of thenanowire-based semiconductor device 100 of FIG. 1A, as taken along thea-a′ axis. FIG. 1B′ illustrates a cross-sectional view of thenanowire-based semiconductor device 100′ of FIG. 1A, as taken along thea-a′ axis.

Referring to FIG. 1A, a semiconductor device 100 or 100′ includes one ormore vertically stacked nanowires (104 set) disposed above a crystallinesubstrate 102. Embodiments herein are targeted at both multiple wiredevices and single wire devices. As an example, a three nanowire-baseddevice 100 (or 100′) having nanowires 104A, 104B and 104C is shown. Forconvenience of description, nanowire 104A is used as an example wheredescription is focused on only one of the nanowires. It is to beunderstood that where attributes of one nanowire are described,embodiments based on a plurality of nanowires may have the sameattributes for each of the nanowires.

In an embodiment, a common crystalline substrate 102 has disposedthereon devices with differing global crystal orientation and/ormaterial composition. For example, semiconductor device 100 and 100′ maybe included on the same substrate 102. The devices are elaborated inFIGS. 1B and 1B′. It is to be understood that embodiments herein maycontemplate any differing global crystal orientation and/or materialcomposition between devices.

Referring to FIG. 1B, a semiconductor structure including both devices100 and 100′ from FIG. 1A includes a first semiconductor device 100having a plurality of nanowires (three: 104A, 104B, and 104C) disposedabove the substrate 102 and stacked in a first vertical plane 105 withan uppermost nanowire 104C and a lowermost nanowire 104A. Referring toFIG. 1B′, a second semiconductor device 100′ has one or more nanowires(three: 104A′, 104B′ and 104C′) disposed above the substrate 102 andstacked in a second vertical plane 105′ with an uppermost nanowire 104C′and a lowermost nanowire 104A′. In an embodiment, as depicted, the firstand second uppermost nanowires 104C and 104C′, respectively, aredisposed in a same plane as one another, orthogonal to the first andsecond vertical planes 105 and 105′. That is, the nanowires 104C and104C′ are equally spaced above the common substrate 102.

As depicted in FIGS. 1A, 1B and 1B′, in an embodiment, each of thenanowires has a discrete channel region 106. The channel region 106 isdiscrete in that it is completely surrounded by the gate electrode stack108 (described below) without any intervening material such asunderlying substrate material or overlying channel fabricationmaterials. Accordingly, in embodiments having a plurality of nanowires104, the channel regions 106 of the nanowires are also discrete relativeto one another, as depicted in FIGS. 1B and 1B′. In one such embodiment,each of the nanowires also includes a pair of discrete source and drainregions 110 and 112, as down in FIG. 1A. That is, the source/drainregions 110/112 are completely surrounded by the contacts 114 (describedbelow) without any intervening material such as underlying substratematerial or overlying channel fabrication materials. Accordingly, insuch an embodiment having a plurality of nanowires 104, the source/drainregions 110/112 of the nanowires are also discrete relative to oneanother. In an alternative such embodiment (not shown), however, thestacks of nanowires include a pair of non-discrete source and drainregions.

In accordance with an embodiment of the present invention, nanowire 104Ais composed of a semiconductor material having a first global crystalorientation. Meanwhile, nanowire 104A′ is composed of a semiconductormaterial having a second global crystal orientation different from thefirst global orientation. In both cases, global orientation is definedalong the Z-direction, e.g., in the same direction as vertical planes105 and 105′, respectively. In accordance with another embodiment of thepresent invention, nanowire 104A is composed of a first semiconductormaterial. Meanwhile, nanowire 104A′ is composed of a secondsemiconductor material different from the first semiconductor material.In accordance with yet another embodiment of the present invention,nanowire 104A is composed of a first semiconductor material and has afirst global crystal orientation. Meanwhile, nanowire 104A′ is composedof a second semiconductor material different from the firstsemiconductor material and has a second global crystal orientationdifferent from the first global orientation.

In an embodiment, the nanowire 104A′ of the semiconductor device 100′ isisolated from the crystalline substrate 102 by an isolation pedestal130′ disposed between the nanowire and the crystalline substrate, asdepicted in FIG. 1B′. In an embodiment, the nanowire 104A of thesemiconductor device 100 is isolated from the crystalline substrate 102by a buried dielectric layer 130 disposed between the nanowire 104A andthe crystalline substrate 102, as depicted in FIG. 1B. In an embodiment,the composition of the buried dielectric layer 130 is essentially thesame as the composition of the isolation pedestal 130′, e.g., both arecomposed of silicon dioxide. In another embodiment, however, thecomposition of the buried dielectric layer 130 is different from thecomposition of the isolation pedestal 130′, e.g., the isolation pedestal130′ is composed of silicon dioxide, while the buried oxide layer 130 iscomposed of silicon nitride or silicon oxynitride. A further isolationportion 131, shown in FIG. 1B′, may be included and may be composed of adielectric material such as, but not limited to, silicon nitride,silicon oxide or silicon oxynitride.

The intervening dielectric portions 130, 130′, or 131 may be an artifactof the fabrication process used to provide devices 100 and 100′ on acommon substrate. It is to be understood that although possibly presentduring partial fabrication, any of the intervening dielectric portions130, 130′, or 131 may be removed prior to completion of a semiconductordevice. Formation of such intervening dielectric portions 130, 130′, or131 is described in greater detail below.

In an embodiment, the term “isolation pedestal” is used to covey adiscrete isolation structure formed at a given time, e.g., a discretestructure formed only under a channel region, or a pair of discretestructures formed only under a pair of source and drain regions, or adiscrete structure formed under a channel region as well as under a pairof source and drain regions. In another embodiment, the term “isolationpedestal” is used to covey a combination of isolation structures formedat different times, e.g., a discrete structure formed under a channelregion in combination with a pair of discrete structures formed, at adifferent time, under a pair of source and drain regions.

In an embodiment, the crystalline substrate 102 has a global orientationthe same as the second global orientation, e.g., the same as the globalorientation of nanowire 104A′ of FIG. 1B′. In one such embodiment, thecrystalline substrate 102 and the semiconductor material of the nanowire104A′ are composed of a Group IV material with a (100) globalorientation, while the semiconductor material of the nanowire 104A ofdevice 100 is composed of a Group IV material with a (110) globalorientation. The Group IV materials may include silicon, silicongermanium, or germanium. In another embodiment, the semiconductormaterial of the nanowire 104A′ is a Group IV material, and thesemiconductor material of the nanowire 104A is a Group IV material or aGroup III-V material.

In an embodiment (not shown), a semiconductor structure includingdevices 100 and 100′ further includes a third semiconductor devicehaving a third nanowire disposed above the crystalline substrate 102.The third nanowire is composed of a semiconductor material having athird global crystal orientation different from the first and secondglobal orientations. The third nanowire is isolated from the crystallinesubstrate 102 by a second isolation pedestal disposed between the thirdnanowire and the crystalline substrate 102.

In another embodiment (not shown), a semiconductor structure includingdevices 100 and 100′ further includes a third semiconductor devicehaving a third nanowire disposed above the crystalline substrate 102.The third nanowire is composed of a third semiconductor materialdifferent from the first and second semiconductor materials. The thirdnanowire is isolated from the crystalline substrate 102 by a secondisolation pedestal disposed between the third nanowire and thecrystalline substrate 102. More general embodiments follow below.

Substrate 102 may be composed of a material suitable for semiconductordevice fabrication. In one embodiment, substrate 102 includes a lowerbulk substrate composed of a single crystal of a material which mayinclude, but is not limited to, silicon, germanium, silicon-germanium ora III-V compound semiconductor material. An upper insulator layercomposed of a material which may include, but is not limited to, silicondioxide, silicon nitride or silicon oxy-nitride is disposed on the lowerbulk substrate. Thus, the structure 100 may be fabricated from astarting semiconductor-on-insulator substrate or may be formed to havesuch an insulating layer during fabrication of the nanowires, asdescribed in greater detail below.

Alternatively, the structure 100 is formed, at least in part, directlyfrom a bulk substrate and local oxidation is used to form electricallyinsulative portions in place of the above described upper insulatorlayer. In another alternative embodiment, the structure 100 is formeddirectly from a bulk substrate and doping is used to form electricallyisolated active regions, such as nanowires, thereon. In one suchembodiment, the first nanowire (i.e., proximate the substrate) is in theform of an omega-FET type structure.

In an embodiment, the nanowires 104 may be sized as wires or ribbons,and may have squared-off or rounder corners. In an embodiment, thenanowires 104 are composed of a material such as, but not limited to,silicon, germanium, or a combination thereof. In one such embodiment,the nanowires are single-crystalline. For example, for a siliconnanowire 104, a single-crystalline nanowire may be based from a (100)global orientation, e.g., with a <100> plane in the z-direction. In anembodiment, the dimensions of the nanowires 104, from a cross-sectionalperspective, are on the nano-scale. For example, in a specificembodiment, the smallest dimension of the nanowires 104 is less thanapproximately 20 nanometers. In an embodiment, the nanowires 104 arecomposed of a strained material, particularly in the channel regions106. The width and height of each of the channel regions 106 is shown asapproximately the same in FIGS. 1B and 1B′, however, they need not be.For example, in another embodiment (not shown), the width of thenanowires 104 is substantially greater than the height. In a specificembodiment, the width is approximately 2-10 times greater than theheight. Nanowires with such geometry may be referred to as nanoribbons.In an alternative embodiment (also not shown), the nanoribbons areoriented vertically. That is, each of the nanowires 104 has a width anda height, the width substantially less than the height.

Referring to FIGS. 1A, 1B and 1B′, in an embodiment, the semiconductordevices 100 or 100′ further include respective gate electrode stacks 108or 108′ surrounding a portion of each of the plurality of nanowires ofthe device. In one such embodiment, the gate electrode stacks 108 or108′ each include a gate dielectric layer and a gate electrode layer(not shown). In an embodiment, the gate electrode of gate electrodestack 108 or 108′ is composed of a metal gate and the gate dielectriclayer is composed of a high-K material. For example, in one embodiment,the gate dielectric layer is composed of a material such as, but notlimited to, hafnium oxide, hafnium oxy-nitride, hafnium silicate,lanthanum oxide, zirconium oxide, zirconium silicate, tantalum oxide,barium strontium titanate, barium titanate, strontium titanate, yttriumoxide, aluminum oxide, lead scandium tantalum oxide, lead zinc niobate,or a combination thereof. Furthermore, a portion of gate dielectriclayer may include a layer of native oxide formed from the top few layersof the nanowire 104. In an embodiment, the gate dielectric layer iscomposed of a top high-k portion and a lower portion composed of anoxide of a semiconductor material. In one embodiment, the gatedielectric layer is composed of a top portion of hafnium oxide and abottom portion of silicon dioxide or silicon oxy-nitride.

In one embodiment, the gate electrode is composed of a metal layer suchas, but not limited to, metal nitrides, metal carbides, metal silicides,metal aluminides, hafnium, zirconium, titanium, tantalum, aluminum,ruthenium, palladium, platinum, cobalt, nickel or conductive metaloxides. In a specific embodiment, the gate electrode is composed of anon-workfunction-setting fill material formed above a metalworkfunction-setting layer.

Referring again to FIG. 1A, in an embodiment, the semiconductor devices100 or 100′ further first and second contacts 114 surrounding respectiveportions of each of the plurality of nanowires 104. The contacts 114are, in an embodiment, fabricated from a metal species. The metalspecies may be a pure metal, such as nickel or cobalt, or may be analloy such as a metal-metal alloy or a metal-semiconductor alloy (e.g.,such as a silicide material).

In an embodiment, the semiconductor devices 100 or 100′ further includefirst and second spacers 116 disposed between the gate electrode stack108 and the first and second contacts 114, respectively, as depicted inFIG. 1A. As described above, the channel regions and the source/drainregions of the nanowires 104 are, in at least several embodiments, madeto be discrete. However, not all regions of the nanowires 104 need be,or even can be made to be discrete. For example, nanowires 104A-104C maynot be discrete at the location under spacers 116. In one embodiment,the stack of nanowires 104A-104C have intervening semiconductor materialthere between, such as silicon germanium intervening between siliconnanowires, or vice versa. Thus, in an embodiment, a portion of theplurality of vertically stacked nanowires under one or both of thespacers is non-discrete. In an embodiment, the spacers 116 are composedof an insulative dielectric material such as, but not limited to,silicon dioxide, silicon oxy-nitride or silicon nitride.

Although the device 100 or 100′ described above is for a single device,e.g., an NMOS or a PMOS device, a CMOS architecture may also be formedto include both NMOS and PMOS nanowire-based channel devices disposed onor above the same substrate. In an embodiment, referring to FIGS. 1B and1B′, the first and second vertical planes 105 and 105′, respectively,are parallel to one another.

As an example of an approach to forming devices, such as devices 100 and100′, on a common substrate, FIGS. 2A-2J illustrate cross-sectionalviews representing various operations in a method of fabricating ananowire semiconductor structure, in accordance with an embodiment ofthe present invention.

Referring to FIG. 2A, a process begins with two active layers (may bereferred to as two substrates), namely a crystalline substrate 202 and acrystalline active layer 206, separated by a dielectric layer 204. In anembodiment, the substrate 202 is a (100) silicon substrate, thecrystalline active layer is a (110) silicon layer, e.g. approximately 10nanometers thick, and the dielectric layer 204 is a thin silicon dioxide(SiO₂) buried oxide layer (BOX layer). It is to be understood thatvariable BOX and/or top silicon layer thicknesses may be used as needed.Also, different types of orientation in the substrate and in the topsilicon layer may be used. Substrates and layers may be strained or notstrained. Materials may instead be silicon germanium (SiGe), germanium(Ge) or a III-V or other material. Substrates and layers may be doped(e.g., carbon-doped silicon, or P-doped silicon, or B-doped silicon, ormay not be doped.

Referring to FIG. 2B, a mask layer 208 is formed on one side of thestructure of FIG. 2A. The exposed portion is then etched etch down belowthe dielectric layer 204. A spacer 210 is then formed, e.g., bydepositing a dielectric layer and etching it, as depicted in FIG. 2C.Referring to FIG. 2D, epitaxial growth of a seed layer 212, e.g., asilicon seed layer 212, is performed on the exposed portions ofsubstrate 202. Alternatively, a silicon germanium and silicon layer maybe formed on top of the (100) silicon, followed by stripping of the masklayer 208.

Referring to FIG. 2E, the mask layer 208 is removed and the spacer 210is recessed. Alternatively, thicker epitaxial layer may be formed andplanarized to expose the active layer 206. Alternatively, the spacer maybe reformed on a SiGe/Si sidewall and then, by masking the (100) side, aSiGe/Si stack may be formed on the (110) side and then planarized or themask layer 208 removed. Referring to FIG. 2F, a stack composed of asilicon germanium layer 214 and a silicon layer 216 is epitaxilly grownas seeding from the substrate 202. The silicon germanium layer 214 andthe silicon layer 216 both have a (100) portion and a (110) portionwith, potentially a defective zone grown at the respective (100) and(110) boundaries. The defective zones may be etched out duringsubsequent fin etch.

Referring to FIG. 2G, fins 220 and 222 are formed by etching usingmasking layer 218 formed in association with FIG. 2F. Also, spacers 224are formed on the sidewalls of fins 220 and 222. Then, the fin 222 isetched down further to reveal substrate 202, as depicted in FIG. 2H.Referring to FIG. 2I, an under fin oxidation (UFO) process is performedto form an isolation pedestal 226 under fin 222. An additionaldielectric portion 228 may be formed by deposition and planarzation(e.g., by etching) and spacers 224 and mask layer 218 may be removed, asdepicted in FIG. 2J.

Referring again to FIG. 2I, in an embodiment, the exposed portions oflayer 212 along with a top portion of substrate 202 are oxidized to formthe isolation pedestal 226 by “under fin oxidation” (UFO). In anembodiment, the use of spacers may be required if a same or likematerial is being oxidized, and may even be included if non-likematerials are used. In an embodiment, an oxidizing atmosphere or anadjacent oxidizing material may be used for UFO. However, in anotherembodiment, oxygen implant is used. In some embodiments, a portion of amaterial is recessed prior to UFO which may reduce the extent ofso-called birds-beak formation during oxidation. Thus, the oxidation maybe performed directly, by recessing first, or by oxygen implant, or acombination thereof.

First and second semiconductor devices may then be formed from the firstand second fins 220 and 222, respectively. In an embodiment, forming thefirst semiconductor device includes forming a plurality of nanowireshaving discrete portions, and forming the second semiconductor deviceincludes forming one or more nanowires also having discrete portions.The wires may be made discrete by having gate placeholders in place orby having source and drain regions strapped down, or both at differentprocessing stages, and then removing the silicon germanium layer. In anembodiment, a PMOS device is formed from the (110) silicon fin 220,while an NMOS device is formed from the (100) silicon fin 222.

As an example of another approach to forming devices, such as devices100 and 100′, on a common substrate, FIGS. 3A-3K illustratecross-sectional views representing various operations in a method offabricating another nanowire semiconductor structure, in accordance withanother embodiment of the present invention.

Referring to FIG. 3A, a process begins with three active layers (may bereferred to as three substrates), namely a crystalline substrate 302, afirst crystalline active layer 306, and a second crystalline activelayer 310, each separated by a dielectric layer 304 or 308. In anembodiment, the substrate 302 is a (100) silicon substrate, the firstcrystalline active layer is a (110) silicon layer, e.g. approximately 10nanometers thick, the second crystalline active layer is a (111) siliconlayer, e.g. approximately 10 nanometers thick, and the dielectric layers304 and 308 are thin silicon dioxide (SiO₂) buried oxide layers (BOXlayers). It is to be understood that variable BOX and/or top siliconlayer thicknesses may be used as needed. Also, different types oforientation in the substrate and in the top silicon layer may be used.Substrates and layers may be strained or not strained. Materials mayinstead be silicon germanium (SiGe), germanium (Ge) or a III-V or othermaterial. Substrates and layers may be doped (e.g., carbon-dopedsilicon, or P-doped silicon, or B-doped silicon, or may not be doped.

Referring to FIG. 3B, a mask layer 312 is formed on one side of thestructure of FIG. 3A. The exposed portion is then etched etch down belowthe dielectric layer 308. A spacer 314 is then formed, e.g., bydepositing a dielectric layer and etching it. Epitaxial growth of a seedlayer 316, e.g., a silicon seed layer 316, is performed on the exposedportions of first crystalline active layer 306, as depicted in FIG. 3C.Referring to FIG. 3D, a second mask layer 318 is formed. The exposedportion is then etched etch down below the dielectric layer 304. Aspacer 320 is then formed, e.g., by depositing a dielectric layer andetching it. Epitaxial growth of a seed layer 322, e.g., a silicon seedlayer 322, is performed on the exposed portions of the substrate 302, asdepicted in FIG. 3E.

Referring to FIG. 3F, the mask layers 312 and 318 are removed and thespacers 320 and 314 are recessed. Referring to FIG. 3G, a stack composedof a silicon germanium layer 324 and a silicon layer 326 is epitaxillygrown as seeding from the substrate 302. The silicon germanium layer 324and the silicon layer 326 both have a (100) portion, a (110) portion,and a (111) portion with, potentially a defective zone grown at therespective (100) and (110) boundaries and at the respective (110) and(111) boundaries. The defective zones may be etched out duringsubsequent fin etch.

Referring to FIG. 3H, fins 328, 330, and 332 are formed by etching usingmasking layer 334 formed in association with FIG. 3G. Also, spacers 336are formed on the sidewalls of fins 328, 330, and 332. Then, the fins330 and 332 are etched down further to reveal respective portions oflayers 316 and 322, as depicted in FIG. 3I. Referring to FIG. 3J, anunder fin oxidation (UFO) process is performed to form isolationpedestal 338 under fin 332 and isolation pedestal 340 under fin 330. Anadditional dielectric portion 342 may be formed by deposition andplanarzation (e.g., by etching) and spacers 336 and mask layer 334 maybe removed, as depicted in FIG. 3K. First, second and thirdsemiconductor devices may then be formed from the first, second andthird fins 328, 330, and 332, respectively.

In another aspect, devices with semiconductor body crystal orientationor material composition modulation on a common substrate are provided byapproaches described herein. For example, FIG. 4A illustrates athree-dimensional cross-sectional view of semiconductor body-basedsemiconductor devices, in accordance with an embodiment of the presentinvention. FIG. 4B illustrates a cross-sectional view of a semiconductorbody-based semiconductor device of FIG. 4A, as taken along the a-a′axis, in accordance with an embodiment of the present invention. FIG.4B′ illustrates a cross-sectional view of another semiconductorbody-based semiconductor device of FIG. 4A, as taken along the a-a′axis, in accordance with another embodiment of the present invention.

Referring to FIG. 4A, a semiconductor device 400 or 400′ includes asemiconductor body 404 or 404′ disposed above a crystalline substrate402. Embodiments herein are targeted at both multiple wire devices andsingle wire devices. In an embodiment, a common crystalline substrate402 has disposed thereon devices with differing global crystalorientation and/or material composition.

For example, semiconductor device 400 and 400′ may be included on thesame substrate 402. The devices are elaborated in FIGS. 4B and 4B′. Itis to be understood that embodiments herein may contemplate anydiffering global crystal orientation and/or material composition betweendevices. Referring to FIG. 4B, a semiconductor structure including bothdevices 400 and 400′ from FIG. 4A includes a first semiconductor device400 having a semiconductor body 404 disposed above the substrate 402.Referring to FIG. 4B′, a second semiconductor device 400′ has asemiconductor body 404′ disposed above the substrate 402. Thesemiconductor bodies 404 and 404′ include source and drain portions 406and 406′, respectively, as well as channel portions.

In accordance with an embodiment of the present invention, semiconductorbody 404 is composed of a semiconductor material having a first globalcrystal orientation. Meanwhile, semiconductor body 404′ is composed of asemiconductor material having a second global crystal orientationdifferent from the first global orientation. In both cases, globalorientation is defined along the Z-direction, as depicted in FIGS. 4Aand 4B′. In accordance with another embodiment of the present invention,semiconductor body 404 is composed of a first semiconductor material.Meanwhile, semiconductor body 404′ is composed of a second semiconductormaterial different from the first semiconductor material. In accordancewith yet another embodiment of the present invention, nanowiresemiconductor body 404 is composed of a first semiconductor material andhas a first global crystal orientation. Meanwhile, semiconductor body404′ is composed of a second semiconductor material different from thefirst semiconductor material and has a second global crystal orientationdifferent from the first global orientation.

In an embodiment, the semiconductor body 404′ of the semiconductordevice 400′ is isolated from the crystalline substrate 402 by anisolation pedestal 430′ disposed between the semiconductor body 404′ andthe crystalline substrate 402, as depicted in FIG. 4B′. In anembodiment, the semiconductor body 404 of the semiconductor device 400is isolated from the crystalline substrate 402 by a buried dielectriclayer 430 disposed between the semiconductor body 404 and thecrystalline substrate 402, as depicted in FIG. 4B.

In an embodiment, the composition of the buried dielectric layer 430 isessentially the same as the composition of the isolation pedestal 430′,e.g., both are composed of silicon dioxide. In another embodiment,however, the composition of the buried dielectric layer 430 is differentfrom the composition of the isolation pedestal 430′, e.g., the isolationpedestal 430′ is composed of silicon dioxide, while the buried oxidelayer 430 is composed of silicon nitride or silicon oxynitride. Afurther isolation portion 431, shown in FIG. 4B′, may be included andmay be composed of a dielectric material such as, but not limited to,silicon nitride, silicon oxide or silicon oxynitride.

The intervening dielectric portions 430, 430′, or 431 may be an artifactof the fabrication process used to provide devices 400 and 400′ on acommon substrate. It is to be understood that although possibly presentduring partial fabrication, any of the intervening dielectric portions430, 430′, or 431 may be removed prior to completion of a semiconductordevice. Formation of such intervening dielectric portions 430, 430′, or431 is described in greater detail below.

In an embodiment, the term “isolation pedestal” is used to covey adiscrete isolation structure formed at a given time, e.g., a discretestructure formed only under a channel region, or a pair of discretestructures formed only under a pair of source and drain regions, or adiscrete structure formed under a channel region as well as under a pairof source and drain regions. In another embodiment, the term “isolationpedestal” is used to covey a combination of isolation structures formedat different times, e.g., a discrete structure formed under a channelregion in combination with a pair of discrete structures formed, at adifferent time, under a pair of source and drain regions.

In an embodiment, the crystalline substrate 402 has a global orientationthe same as the second global orientation, e.g., the same as the globalorientation of semiconductor body 404′ of FIG. 4B′. In one suchembodiment, the crystalline substrate 402 and the semiconductor materialof the semiconductor body 404′ are composed of a Group IV material witha (100) global orientation, while the semiconductor material of thesemiconductor body 404 of device 400 is composed of a Group IV materialwith a (110) global orientation. The Group IV materials may includesilicon, silicon germanium, or germanium. In another embodiment, thesemiconductor material of the semiconductor body 404′ is a Group IVmaterial, and the semiconductor material of the semiconductor body 404is a Group IV material or a Group III-V material.

In an embodiment (not shown), a semiconductor structure includingdevices 400 and 400′ further includes a third semiconductor devicehaving a third semiconductor body disposed above the crystallinesubstrate 402. The third semiconductor body is composed of asemiconductor material having a third global crystal orientationdifferent from the first and second global orientations. The thirdsemiconductor body is isolated from the crystalline substrate 402 by asecond isolation pedestal disposed between the third semiconductor bodyand the crystalline substrate 402.

In another embodiment (not shown), a semiconductor structure includingdevices 400 and 400′ further includes a third semiconductor devicehaving a third semiconductor body disposed above the crystallinesubstrate 402. The third semiconductor body is composed of a thirdsemiconductor material different from the first and second semiconductormaterials. The third semiconductor body is isolated from the crystallinesubstrate 402 by a second isolation pedestal disposed between the thirdsemiconductor body and the crystalline substrate 402. More generalembodiments follow below.

Substrate 402 and, if originally formed from the substrate 402,semiconductor bodies 404 or 404′ may be composed of a semiconductormaterial that can withstand a manufacturing process and in which chargecan migrate. In an embodiment, substrate 402 is composed of acrystalline silicon, silicon/germanium or germanium layer doped with acharge carrier, such as but not limited to phosphorus, arsenic, boron ora combination thereof. In one embodiment, the concentration of siliconatoms in substrate 102 is greater than 97%. In another embodiment,substrate 402 is composed of an epitaxial layer grown atop a distinctcrystalline substrate, e.g. a silicon epitaxial layer grown atop aboron-doped bulk silicon mono-crystalline substrate. Substrate 402 mayalso include an insulating layer disposed in between a bulk crystalsubstrate and an epitaxial layer to form, for example, asilicon-on-insulator substrate. In an embodiment, the insulating layeris composed of a material such as, but not limited to, silicon dioxide,silicon nitride, silicon oxy-nitride or a high-k dielectric layer.Substrate 402 may alternatively be composed of a group III-V material.In an embodiment, substrate 402 is composed of a III-V material such as,but not limited to, gallium nitride, gallium phosphide, galliumarsenide, indium phosphide, indium antimonide, indium gallium arsenide,aluminum gallium arsenide, indium gallium phosphide, or a combinationthereof. In one embodiment, substrate 402 is composed of crystallinesilicon and the charge-carrier dopant impurity atoms are one such as,but not limited to, boron, arsenic, indium or phosphorus. In anotherembodiment, substrate 402 is composed of a III-V material and thecharge-carrier dopant impurity atoms are ones such as, but not limitedto, carbon, silicon, germanium, oxygen, sulfur, selenium or tellurium.In another embodiment, the semiconductor substrate and, hence, thesemiconductor body 404 or 404′ is undoped or only lightly doped.

In an embodiment, the semiconductor device 400 or 400′ is a non-planardevice such as, but not limited to, a fin-FET or a tri-gate device. Insuch an embodiment, the semiconducting channel region is composed of oris formed in a three-dimensional body. In one such embodiment, the gateelectrode stack 408 or 408′ surrounds at least a top surface and a pairof sidewalls of the three-dimensional body, as depicted in FIGS. 4B and4B′. In another embodiment, at least the channel region is made to be adiscrete three-dimensional body, such as in a gate-all-around device. Inone such embodiment, the gate electrode stack 408 or 408′ completelysurrounds the channel region.

In the case of a three-dimensional body 404 or 404′, whether isolated ornot, the three-dimensional body 404 or 404′ may be fabricated from abulk substrate. Alternatively, the three-dimensional body 404 or 404′may be fabricated from a starting semiconductor-on-insulator substrate.In another embodiment, the three-dimensional body 404 or 404′ is formeddirectly from a bulk substrate and local oxidation is used to formelectrically insulative underlying regions. In another alternativeembodiment, the device 400 or 400′ is formed directly from a bulksubstrate and doping is used to form electrically isolated activeregions. In one such embodiment, the an omega-FET type structure isformed.

As mentioned above, referring to FIGS. 4A, 4B and 4B′, in an embodiment,the semiconductor devices 400 or 400′ further include respective gateelectrode stacks 408 or 408′ at least partially surrounding a portion ofthe semiconductor body 404 or 404′ of the device. In one suchembodiment, the gate electrode stacks 408 or 408′ each include a gatedielectric layer and a gate electrode layer (not shown). In anembodiment, the gate electrode of gate electrode stack 408 or 408′ iscomposed of a metal gate and the gate dielectric layer is composed of ahigh-K material. For example, in one embodiment, the gate dielectriclayer is composed of a material such as, but not limited to, hafniumoxide, hafnium oxy-nitride, hafnium silicate, lanthanum oxide, zirconiumoxide, zirconium silicate, tantalum oxide, barium strontium titanate,barium titanate, strontium titanate, yttrium oxide, aluminum oxide, leadscandium tantalum oxide, lead zinc niobate, or a combination thereof.Furthermore, a portion of gate dielectric layer may include a layer ofnative oxide formed from the top few layers of the semiconductor body404 or 404′. In an embodiment, the gate dielectric layer is composed ofa top high-k portion and a lower portion composed of an oxide of asemiconductor material. In one embodiment, the gate dielectric layer iscomposed of a top portion of hafnium oxide and a bottom portion ofsilicon dioxide or silicon oxy-nitride.

In one embodiment, the gate electrode is composed of a metal layer suchas, but not limited to, metal nitrides, metal carbides, metal silicides,metal aluminides, hafnium, zirconium, titanium, tantalum, aluminum,ruthenium, palladium, platinum, cobalt, nickel or conductive metaloxides. In a specific embodiment, the gate electrode is composed of anon-workfunction-setting fill material formed above a metalworkfunction-setting layer.

In an embodiment, although not shown, the semiconductor devices 400 or400′ further include a pair of contacts at least partially surroundingrespective portions of the semiconductor body 404 or 404′, e.g., atleast partially surrounding source and drain regions 406 or 406′. Thecontacts are, in an embodiment, fabricated from a metal species. Themetal species may be a pure metal, such as nickel or cobalt, or may bean alloy such as a metal-metal alloy or a metal-semiconductor alloy(e.g., such as a silicide material). In an embodiment, the semiconductordevices 400 or 400′ further include spacers 416 (as depicted in FIG.4A). The spacers 416 may be disposed between the gate electrode stack408 or 408′ and a pair of contacts at least partially surrounding sourceand drain regions 406 or 406′. In an embodiment, the spacers 416 arecomposed of an insulative dielectric material such as, but not limitedto, silicon dioxide, silicon oxy-nitride or silicon nitride.

Semiconductor device 400 or 400′ may be any semiconductor deviceincorporating a gate, a channel region and a pair of source/drainregions. In an embodiment, semiconductor device 400 or 400′ is one suchas, but not limited to, a MOS-FET, a memory transistor, or aMicroelectromechanical System (MEMS). In one embodiment, semiconductordevice 400 or 400′ is a three-dimensional MOS-FET and is an isolateddevice or is one device in a plurality of nested devices. As will beappreciated for a typical integrated circuit, both N- and P-channeltransistors may be fabricated on a single substrate to form a CMOSintegrated circuit, a semiconductor structure for which is described ingreater detail below.

Although the device 400 or 400′ described above is for a single device,e.g., an NMOS or a PMOS device, a CMOS architecture may also be formedto include both NMOS and PMOS channel devices disposed on or above thesame substrate. In an embodiment, semiconductor devices 400 and 400′ areformed on a common substrate. Semiconductor body isolation may, in anembodiment, be achieved by initiating fabrication on a bulk siliconsubstrate and patterning a fin using a spacer patterning technique byselective masking an area to be etched. The etching of the fin isperformed to the depth needed for subfin isolation (e.g., an operationthat sets the height as active) for a particular structure.

As an example of an approach to forming devices, such as devices 400 and400′, on a common substrate, FIGS. 5A-5I illustrate cross-sectionalviews representing various operations in a method of fabricating asemiconductor body-based semiconductor structure, in accordance with anembodiment of the present invention.

Referring to FIG. 5A, a process begins with two active layers (may bereferred to as two substrates), namely a crystalline substrate 502 and acrystalline active layer 506, separated by a dielectric layer 504. In anembodiment, the substrate 502 is a (100) silicon substrate, thecrystalline active layer is a (110) silicon layer, e.g. approximately 10nanometers thick, and the dielectric layer 504 is a thin silicon dioxide(SiO₂) buried oxide layer (BOX layer). It is to be understood thatvariable BOX and/or top silicon layer thicknesses may be used as needed.Also, different types of orientation in the substrate and in the topsilicon layer may be used. Substrates and layers may be strained or notstrained. Materials may instead be silicon germanium (SiGe), germanium(Ge) or a III-V or other material. Substrates and layers may be doped(e.g., carbon-doped silicon, or P-doped silicon, or B-doped silicon, ormay not be doped.

Referring again to FIG. 5A, a mask layer 508 is formed on one side ofthe structure. The exposed portion is then etched etch down below thedielectric layer 504. A spacer 510 is then formed, e.g., by depositing adielectric layer and etching it, as depicted in FIG. 5B. Referring toFIG. 5C, epitaxial growth of a seed layer 512, e.g., a silicon seedlayer 512, is performed on the exposed portions of substrate 502.Referring to FIG. 5D, the mask layer 508 is removed and the spacer 510is recessed. Referring to FIG. 5E, a silicon layer 516 is epitaxillygrown as seeding from the substrate 502. The silicon layer 516 has a(100) portion and a (110) portion with, potentially, a defective zonegrown at the (100) and (110) boundary. The defective zone may be etchedout during subsequent fin etch.

Referring to FIG. 5F, fins 520 and 522 are formed by etching usingmasking layer 518 formed in association with FIG. 5E. Also, spacers 524are formed on the sidewalls of fins 520 and 522. Then, the fin 522 isetched down further to reveal substrate 502, as depicted in FIG. 5G.Referring to FIG. 5H, an under fin oxidation (UFO) process is performedto form an isolation pedestal 526 under fin 522. An additionaldielectric portion 528 may be formed by deposition and planarzation(e.g., by etching) and spacers 524 and mask layer 518 may be removed, asdepicted in FIG. 5I.

First and second semiconductor devices may then be formed from the firstand second fins 520 and 522, respectively. In an embodiment, a PMOSdevice is formed from the (110) silicon fin 520, while an NMOS device isformed from the (100) silicon fin 522.

As an example of another approach to forming devices, such as devices400 and 400′, on a common substrate, FIGS. 6A-6I illustratecross-sectional views representing various operations in a method offabricating another semiconductor body-based semiconductor structure, inaccordance with another embodiment of the present invention.

Referring to FIG. 6A, a process begins with two active layers (may bereferred to as two substrates), namely a crystalline substrate 602 and acrystalline III-V material layer 606, separated by a dielectric layer604. In an embodiment, the substrate 602 is a (100) silicon substrateand the dielectric layer 604 is a thin silicon dioxide (SiO₂) buriedoxide layer (BOX layer). It is to be understood that variable BOX and/ortop III-V material layer thicknesses may be used as needed. Also,different types of orientation in the substrate and in the top III-Vmaterial layer may be used. Substrates and layers may be strained or notstrained. Substrates and layers may be doped or may not be doped.

Referring again to FIG. 6A, a mask layer 608 is formed on one side ofthe structure. The exposed portion is then etched etch down below thedielectric layer 604. A spacer 610 is then formed, e.g., by depositing adielectric layer and etching it, as depicted in FIG. 6B. Referring toFIG. 6C, epitaxial growth of a seed layer 612, e.g., a silicon seedlayer 612, is performed on the exposed portions of substrate 602.Referring to FIG. 6D, the mask layer 608 is removed and the spacer 610is recessed.

Referring to FIG. 6E, a masking layer 618 is formed. Then, fins 620 and622 are formed by etching using masking layer 618, as depicted in FIG.6F. Also, spacers 624 are formed on the sidewalls of fins 620 and 622.Then, the fin 622 is etched down further to reveal substrate 602, asdepicted in FIG. 6G. Referring to FIG. 6H, an under fin oxidation (UFO)process is performed to form an isolation pedestal 626 under fin 622. Anadditional dielectric portion 628 may be formed by deposition andplanarzation (e.g., by etching) and spacers 624 and mask layer 618 maybe removed, as depicted in FIG. 6I.

First and second semiconductor devices may then be formed from the firstand second fins 620 and 622, respectively. In an embodiment, a PMOSdevice is formed from the silicon fin 622, while an NMOS device isformed from the III-V fin 620. In this way, both silicon and III-V finsare formed on the same wafer. In an embodiment, this approach not onlyhigh quality silicon formation, but also defect free single crystalSiGe, Ge or III-V on the same wafer, with isolation from a bulksubstrate. Many embodiments are possible with SiGe, Ge or any othersubstrate material disposed on an oxide wafer in the manner describedabove.

One or more embodiments of the present invention include use of an underfin oxide (UFO) process methodology to isolate an active diffusion area.Under conventional processing of trigate or FIN-FET transistors frombulk silicon substrates, sub-FIN leakage of the resulting devices mayoccur. Such leakage may render difficult the targeting and controllingof I_(off) (off-state source and drain leakage). The leakage may beeffectively suppressed by the introduction of an insulating layer at thebottom of the fin, in the area that has poor or no gate control. Thus,in an embodiment, and as described above, the introduction of aninsulating material may enable an easy targeting of channel dopingreduction to achieve a lightly doped or fully undoped channel device.Having a buried oxide in the sub-fin region may also relax theconflicting constraints and simultaneously enable a low-doped fin withhigh mobility, excellent device electrostatics and elimination of thesubstrate junction leakage. Also, the presence of an oxide under thesource and drain regions may significantly reduce junction leakage. Theprocess flows described herein may be applicable to nanowire, tri-gateand fin-FET type devices, or subsets thereof such as omega-gate, pi gateor fin with gate all around transistors.

One or more embodiments of the present invention provide a“cost-effective” solution to improving transistor performance andreducing stand-by power, e.g., for system-on-chip (SOC) ultra-low powerdevices which are limited by junction leakage in standby mode. Althoughsuch benefits may also be achieved by doping very highly the subfinregion, such doping is difficult to perform without affecting thechannel doping and, hence, impacting mobility. Alternatively, aprefabricated SOI substrate may be used but typically requires higherfabrication costs. Accordingly, one ore more embodiments involve thefabrication of, e.g., nanowires fin-FETs or trigate devices based onfins with an isolation pedestal and/or a buried oxide layer. In one suchembodiment, the isolation pedestal or buried oxide layer isolates theactive fin channel from the underlying substrate. Such approaches may becost-effective solutions since they may begin with bulk substrates andthe isolating of the active fin from the substrate may be performedusing localized oxidation in the subfin region.

FIG. 7 illustrates exemplary process flows for forming a wafer having acrystalline substrate and one or more separate crystalline activelayers, in accordance with an embodiment of the present invention.Referring to FIG. 7, process flow 700 is based on a silicon-on-insulator(SOI) approach and includes a donor wafer flow 702, a handle wafer flow704, and a bonding flow 706. In one embodiment, a wafer 708 having acrystalline substrate and one separate crystalline active layer isformed (also referred to as a two substrate wafer). In anotherembodiment, a wafer 710 having a crystalline substrate and two separatecrystalline active layers is formed (also referred to as a threesubstrate wafer).

FIG. 8 illustrates a computing device 800 in accordance with oneimplementation of the invention. The computing device 800 houses a board802. The board 802 may include a number of components, including but notlimited to a processor 804 and at least one communication chip 806. Theprocessor 804 is physically and electrically coupled to the board 802.In some implementations the at least one communication chip 806 is alsophysically and electrically coupled to the board 802. In furtherimplementations, the communication chip 806 is part of the processor804.

Depending on its applications, computing device 800 may include othercomponents that may or may not be physically and electrically coupled tothe board 802. These other components include, but are not limited to,volatile memory (e.g., DRAM), non-volatile memory (e.g., ROM), flashmemory, a graphics processor, a digital signal processor, a cryptoprocessor, a chipset, an antenna, a display, a touchscreen display, atouchscreen controller, a battery, an audio codec, a video codec, apower amplifier, a global positioning system (GPS) device, a compass, anaccelerometer, a gyroscope, a speaker, a camera, and a mass storagedevice (such as hard disk drive, compact disk (CD), digital versatiledisk (DVD), and so forth).

The communication chip 806 enables wireless communications for thetransfer of data to and from the computing device 800. The term“wireless” and its derivatives may be used to describe circuits,devices, systems, methods, techniques, communications channels, etc.,that may communicate data through the use of modulated electromagneticradiation through a non-solid medium. The term does not imply that theassociated devices do not contain any wires, although in someembodiments they might not. The communication chip 806 may implement anyof a number of wireless standards or protocols, including but notlimited to Wi-Fi (IEEE 802.11 family), WiMAX (IEEE 802.16 family), IEEE802.20, long term evolution (LTE), Ev-DO, HSPA+, HSDPA+, HSUPA+, EDGE,GSM, GPRS, CDMA, TDMA, DECT, Bluetooth, derivatives thereof, as well asany other wireless protocols that are designated as 3G, 4G, 5G, andbeyond. The computing device 800 may include a plurality ofcommunication chips 806. For instance, a first communication chip 806may be dedicated to shorter range wireless communications such as Wi-Fiand Bluetooth and a second communication chip 806 may be dedicated tolonger range wireless communications such as GPS, EDGE, GPRS, CDMA,WiMAX, LTE, Ev-DO, and others.

The processor 804 of the computing device 800 includes an integratedcircuit die packaged within the processor 804. In some implementationsof the invention, the integrated circuit die of the processor includesone or more devices, such as MOS-FET transistors built in accordancewith implementations of the invention. The term “processor” may refer toany device or portion of a device that processes electronic data fromregisters and/or memory to transform that electronic data into otherelectronic data that may be stored in registers and/or memory.

The communication chip 806 also includes an integrated circuit diepackaged within the communication chip 806. In accordance with anotherimplementation of the invention, the integrated circuit die of thecommunication chip includes one or more devices, such as MOS-FETtransistors built in accordance with implementations of the invention.

In further implementations, another component housed within thecomputing device 800 may contain an integrated circuit die that includesone or more devices, such as MOS-FET transistors built in accordancewith implementations of the invention.

In various implementations, the computing device 800 may be a laptop, anetbook, a notebook, an ultrabook, a smartphone, a tablet, a personaldigital assistant (PDA), an ultra mobile PC, a mobile phone, a desktopcomputer, a server, a printer, a scanner, a monitor, a set-top box, anentertainment control unit, a digital camera, a portable music player,or a digital video recorder. In further implementations, the computingdevice 800 may be any other electronic device that processes data.

Thus, common-substrate semiconductor devices having nanowires orsemiconductor bodies with differing material orientation or compositionand methods to form such common-substrate devices have been disclosed.In an embodiment, a semiconductor structure includes a firstsemiconductor device having a first nanowire or semiconductor bodydisposed above a crystalline substrate. The first nanowire orsemiconductor body is composed of a semiconductor material having afirst global crystal orientation. The semiconductor structure alsoincludes a second semiconductor device having a second nanowire orsemiconductor body disposed above the crystalline substrate. The secondnanowire or semiconductor body is composed of a semiconductor materialhaving a second global crystal orientation different from the firstglobal orientation. The second nanowire or semiconductor body isisolated from the crystalline substrate by an isolation pedestaldisposed between the second nanowire or semiconductor body and thecrystalline substrate. In another embodiment, a semiconductor structureincludes a first semiconductor device having a first nanowire orsemiconductor body disposed above a crystalline substrate. The firstnanowire or semiconductor body is composed of a first semiconductormaterial. The semiconductor structure also includes a secondsemiconductor device having a second nanowire or semiconductor bodydisposed above the crystalline substrate. The second nanowire orsemiconductor body is composed of a second semiconductor materialdifferent from the first semiconductor material. The second nanowire orsemiconductor body is isolated from the crystalline substrate by anisolation pedestal disposed between the second nanowire or semiconductorbody and the crystalline substrate.

What is claimed is:
 1. A semiconductor structure, comprising: a firstsemiconductor device comprising a first nanowire disposed above acrystalline substrate, the first nanowire comprising a firstsemiconductor material; a second semiconductor device comprising asecond nanowire disposed above the crystalline substrate, the secondnanowire comprising a second semiconductor material different from thefirst semiconductor material, and the second nanowire isolated from thecrystalline substrate by an isolation pedestal disposed between thesecond nanowire and the crystalline substrate; and a third semiconductordevice comprising a third nanowire disposed above the crystallinesubstrate, the third nanowire comprising a third semiconductor materialdifferent from the first and second semiconductor materials, the thirdnanowire isolated from the crystalline substrate by a second isolationpedestal disposed between the third nanowire and the crystallinesubstrate, wherein a bottom surface of the first nanowire is co-planarwith a bottom surface of the second nanowire and is co-planar with abottom surface of the third nanowire, and wherein the first nanowire,the second nanowire and the third nanowire are all parallel with oneanother.
 2. The semiconductor structure of claim 1, wherein the firstnanowire of the first semiconductor device is isolated from thecrystalline substrate by a buried dielectric layer disposed between thefirst nanowire and the crystalline substrate.
 3. The semiconductorstructure of claim 2, wherein a composition of the buried dielectriclayer is essentially the same as a composition of the isolationpedestal.
 4. The semiconductor structure of claim 2, wherein acomposition of the buried dielectric layer is different from acomposition of the isolation pedestal.
 5. The semiconductor structure ofclaim 1, wherein the first semiconductor device further comprises one ormore additional nanowires disposed above and stacked in a vertical planewith the first nanowire, the second semiconductor device furthercomprises one or more additional nanowires disposed above and stacked ina vertical plane with the second nanowire, and the third semiconductordevice further comprises one or more additional nanowires disposed aboveand stacked in a vertical plane with the third nanowire.
 6. Thesemiconductor structure of claim 1, wherein the first semiconductordevice further comprises a first gate electrode stack surrounding aportion of the first nanowire, the second semiconductor device furthercomprises a second gate electrode stack surrounding a portion of thesecond nanowire, and the third semiconductor device further comprises athird gate electrode stack surrounding a portion of the third nanowire.7. A semiconductor structure, comprising: a first semiconductor devicecomprising a first semiconductor body disposed above a crystallinesubstrate, the first semiconductor body comprising a first semiconductormaterial; a second semiconductor device comprising a secondsemiconductor body disposed above the crystalline substrate, the secondsemiconductor body comprising a second semiconductor material differentfrom the first semiconductor material, and the second semiconductor bodyisolated from the crystalline substrate by an isolation pedestaldisposed between the second semiconductor body and the crystallinesubstrate; and a third semiconductor device comprising a thirdsemiconductor body disposed above the crystalline substrate, the thirdsemiconductor body comprising a third semiconductor material differentfrom the first and second semiconductor materials, the thirdsemiconductor body isolated from the crystalline substrate by a secondisolation pedestal disposed between the third semiconductor body and thecrystalline substrate, wherein a bottom surface of the firstsemiconductor body is co-planar with a bottom surface of the secondsemiconductor body and is co-planar with a bottom surface of the thirdsemiconductor body, and wherein the first semiconductor body, the secondsemiconductor body and the third semiconductor body are all parallelwith one another.
 8. The semiconductor structure of claim 7, wherein thefirst semiconductor body of the first semiconductor device is isolatedfrom the crystalline substrate by a buried dielectric layer disposedbetween the first semiconductor body and the crystalline substrate. 9.The semiconductor structure of claim 8, wherein a composition of theburied dielectric layer is essentially the same as a composition of theisolation pedestal.
 10. The semiconductor structure of claim 8, whereina composition of the buried dielectric layer is different from acomposition of the isolation pedestal.
 11. The semiconductor structureof claim 7, wherein the first semiconductor device further comprises afirst gate electrode stack surrounding a portion of the firstsemiconductor body, the second semiconductor device further comprises asecond gate electrode stack surrounding a portion of the secondsemiconductor body, and the third semiconductor device further comprisesa third gate electrode stack surrounding a portion of the thirdsemiconductor body.